Polysaccharide nanocomposites in wastewater treatment: A review

Rheological aspects of xanthan gum: Governing factors and applications in water-based drilling fluids and enhanced oil recovery

In the context of a low-carbon future, green, sustainable, and environmentally friendly oilfield development methods have become urgent priorities. The application of bio-based materials in water-based drilling fluids (WBDFs) and enhanced oil recovery (EOR) is emerging as a key strategy for driving sustainable development. Xanthan gum (XG), a natural polysaccharide, has gained significant attention due to its non-toxic, biodegradable, renewable, and environmentally friendly characteristics. Its shear-thinning rheological properties make it particularly suitable for oilfield development. This review summarizes the production, modification, and chemical structure of XG, focusing on key factors influencing the rheological behavior of its aqueous solutions, including shear rate, shear stress, concentration, pH, salinity, temperature, time, and polysaccharide interactions. Additionally, recent advances in XG's application in WBDFs and EOR are discussed. Although XG's viscosity stability and recovery under high-temperature and long-duration conditions present challenges, these issues have been largely addressed through increased salinity and chemical modifications. Finally, this review highlights key future research directions, such as exploring the structure-rheology relationship of XG, polysaccharide interactions, the rheological behavior and sustainability of XG derivatives, and its economic feasibility in oilfield development. These insights aim to improve XG's adaptability to harsh oilfield conditions and guide its use in similar environments.

Simultaneous elimination of cationic dyes from water media by carboxymethyl cellulose-graft-poly(acrylamide)/magnetic biochar nanocomposite hydrogel adsorbent

In this work, the grafting of acrylamide onto CMC was performed by a free radical polymerization method to prepare hydrogel for the elimination of single and simultaneous methylene blue (MB) and methyl violet (MV) -as common textural dyes-from water. Biochar (CL) and magnetic biochar of Luffa Cylindrica (CL-Fe3O4) were integrated into the hydrogel matrix to promote removal performance. CL was prepared using the pyrolysis method and modified using Fe3O4 magnetic nanoparticles by a co-precipitation method. Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and vibration sample magnetometry (VSM) analysis were applied to characterize prepared adsorbents. The maximum removal of single MB and MV occurred at a pH of 9, temperature of 25 °C, adsorbent dose of 1.5 g/L, initial concentration of 10 mg/L, and contact time of 60 min. The maximum removal efficiency under the optimal conditions was determined to be 83.11, 92.89 and 95.01% for single adsorption of MB, 76.09, 85.91 and 90.11% for single adsorption of MV, 66.96, 76.48 and 80.02% for simultaneous adsorption of MB and 60.04, 69.91 and 75.28% for simultaneous adsorption of MV by CMC-g-poly(AAm), CMC-g-poly(AAm)/CL, and CMC-g-poly(AAm)/CL-Fe3O4, respectively. The kinetic and isotherm studies revealed that the pseudo-second-order kinetic model and the Langmuir isotherm model aligned more with the experimental data. Thermodynamic studies showed that the adsorption of dyes takes place spontaneously and exothermically. Therefore, CMC-g-poly(AAm)/CL-Fe3O4 nanocomposite hydrogel could be used for wastewater treatment applications.

A short review on polysaccharide-based nanocomposite adsorbents for separation and biomedical applications

Polysaccharides such as chitosan, alginate, cellulose, and carrageenan have emerged as promising adsorbents due to their biodegradability, abundant availability, and diverse chemical functionality. These biopolymers exhibit promising performance for adsorption of a wide range of pollutants including heavy metals (e.g., lead, cadmium), organic dyes (e.g., methylene blue, methyl orange), and even pathogenic microorganisms. However, inherent hydrophilicity and poor mechanical properties limit their broader application in environmental and biomedical fields. As an effective way to address the issues, recent advancements have focused on the incorporation of nanoparticles (e.g., metal oxides, carbon nanotubes and clays) into polysaccharides to obtain nanocomposite films. Generally, these nanocomposites offer enhanced surface area, tunable porous network, and improved chemical and mechanical resistances for adsorption and biomedical applications. The current review gives a focused overview of the recent progresses in polysaccharide-based nanocomposites, with particular attention to their fabrication methods, adsorption capacity and mechanism, and diverse applications in water purification, drug delivery, and antimicrobial treatments. Critical challenges such as the optimization of nanoparticle dispersion and the environmental impacts of nanocomposite biodegradation are also discussed to pave the road for the future research in this promising field.

Preparation and Heavy Metal Adsorption Performance of 2-Aminopyridine-Modified Sodium Alginate/Polyacrylic Acid Hydrogel

This study utilized the Schiff base reaction as a chemical bonding method to successfully graft 2-aminopyridine onto oxidized sodium alginate, resulting in the formation of modified sodium alginate (OSM). Subsequently, the OSM/polyacrylic acid (OSM/PAA) hydrogel was synthesized via a thermally initiated free radical polymerization process and evaluated as an adsorbent for the removal of heavy metal ions from wastewater. Comprehensive characterization of the prepared samples was performed using FT-IR, SEM, and TGA. The influence of temperature, pH, adsorbent dosage, contact time, and heavy metal ion concentration on the adsorption capacity of the OSM/PAA adsorbent in simulated wastewater was thoroughly investigated. Additionally, a detailed analysis of the adsorption thermodynamics, kinetics, and mechanisms was conducted. Experimental results indicated that at 25 °C, pH 5.0, and an adsorbent dosage of 0.4 g/L, the maximum adsorption capacities of the OSM/PAA hydrogel for Cu(II), Zn(II), and Ni(II) were 367.64 mg/g, 398.4 mg/g, and 409.83 mg/g, respectively. These findings suggest that the adsorption of heavy metal ions by OSM/PAA is a spontaneous, heterogeneous chemical process with significant potential for practical applications in wastewater treatment.

Polysaccharide Hydrogels as Delivery Platforms for Natural Bioactive Molecules: From Tissue Regeneration to Infection Control

Polysaccharide-based hydrogels have emerged as indispensable materials in tissue engineering and wound healing, offering a unique combination of biocompatibility, biodegradability, and structural versatility. Indeed, their three-dimensional polymeric network and high water content closely resemble the natural extracellular matrix, creating a microenvironment for cell growth, differentiation, and tissue regeneration. Moreover, their intrinsic biodegradability, tunable chemical structure, non-toxicity, and minimal immunogenicity make them optimal candidates for prolonged drug delivery systems. Notwithstanding numerous advantages, these polysaccharide-based hydrogels are confronted with setbacks such as variability in material qualities depending on their source, susceptibility to microbial contamination, unregulated water absorption, inadequate mechanical strength, and unpredictable degradation patterns which limit their efficacy in real-world applications. This review summarizes recent advancements in the application of polysaccharide-based hydrogels, including cellulose, starch, pectin, zein, dextran, pullulan and hyaluronic acid as innovative solutions in wound healing, drug delivery, tissue engineering, and regenerative medicine. Future research should concentrate on optimizing hydrogel formulations to enhance their effectiveness in regenerative medicine and antimicrobial therapy.

Co-immobilization of laccase and zinc oxide nanoparticles onto bacterial cellulose to achieve synergistic effect of photo and enzymatic catalysis for biodegradation of favipiravir

The environmental persistence of pharmaceuticals represents a significant threat to aquatic ecosystems and human health, while limitations in conventional wastewater treatment methods underscore the urgent need for innovative and eco-friendly degradation strategies. Photobiocatalytic approaches provide a promising solution for the effective degradation of pharmaceutical contaminants by harnessing the synergistic effects of both photocatalysts and biocatalysts. In this study, we developed a photobiocatalytic composite by co-immobilizing laccase enzyme and zinc oxide nanoparticles on bacterial cellulose synthesized from orange peel waste. The optimal conditions for achieving maximum yield and efficiency of immobilization were investigated and the successful preparation of the composite was confirmed using infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The immobilized laccase showed Km and Vmax values of 0.68 ± 0.23 mM and 5.4 ± 0.86 μmol/min/L, respectively. The prepared composite was efficiently applied for degradation of favipiravir under optimum conditions including pH, temperature, and incubation time values of 4.0, 50 °C, and 90 min, respectively. The presence of ZnO nanoparticles in the structure of the photobiocatalyst significantly decreased the time of removal in comparison with both free and immobilized laccases. Although 80 ± 5.5 % of the enzyme activity was kept after 10 runs, the prepared photobiocatalyst retained 50 ± 4.6 % of its initial activity after 10 independent cycles. The study showed that the synergistic effects of laccase and ZnO nanoparticles possess the potentials to enhance degradation efficiency through combined light-driven and enzymatic approaches.

Cross-linked chitosan/H-ZSM-5 zeolite composite film for chromium removal from aqueous solutions: optimization using response surface methodology and adsorption mechanism assessment

The present work investigates, for the first time, the synthesis of a composite film based on glutaraldehyde-cross-linked chitosan (GA-CS) and a natural zeolite (H-ZSM-5) and its application for the removal of hexavalent chromium (Cr(VI)) from aqueous solutions under wide experimental conditions. The composite film (GA-CS-ZEO) characterization by using various analytical techniques confirms its successful production with promising physical, chemical, and thermal properties. The use of the response surface methodology (RSM) for the optimization of the Cr(VI) adsorption by this composite shows that that the maximum removal efficiency (82.39%) was achieved for a Cr(VI) concentration of 50 mg L-1, an initial pH of 2.0, a contact time of 100 min, and a temperature of 20 °C. Moreover, the analysis of variance (ANOVA) and 3D graphs indicated that the pH and initial Cr(VI) concentration were the main factors that influence the Cr(VI) uptake efficiency. Besides that, the Cr(VI) removal by the GA-CS-ZEO was found to be spontaneous and endothermic and occurs mainly via physical mechanisms involving electrostatic interactions and hydrogen bonding. Regeneration study of the Cr(VI)-loaded composite showed that Cr(VI) can be rapidly and efficiently desorbed by 0.1 M sulfuric acid. The results of the current research work highlight the important adsorption potential of Cr(VI) by the GA-CS-ZEO composite film and underscore its attractiveness and suitability for water treatment applications.

Tailoring of carboxymethyl guar gum hydrogels via gamma irradiation for remarkable removal of cationic and anionic dyes from simulated solutions

Green hydrogels were synthesized from carboxymethyl guar gum (CMGG)-polyacrylic acid (PAAc) via gamma irradiation at doses of 10-40 kGy, they were codes as (CMGG/PAAc). FTIR spectroscopy was applied to confirm the chemical transformation of GG into the hydrogel formulations while the 1HNMR was employed to confirm the successful preparation of CMGG. TGA, XRD, and AFM were used to compare the improved formulation to native and CMGG. The investigated hydrogels were then applied comparatively to remove methylene blue (MB) and methyl orange (MO) dyes from aqueous solution under various operating parameters. In addition, the AFM was used comprehensively to address the adsorption process by comparing the surface topographies, height and roughness measurements between the dry and dye-loaded hydrogel. Four adsorption isotherms were investigated in order to go deep through the adsorption mechanism. These are Langmuir Freundlich, Redlich-Peterson and Jovanovich isotherms. Based on the values of R2 for all the models, it can be assumed that the Langmuir model is best appropriate for the adsorption process and that the dyes were adsorbed onto a homogenous surface. Kinetic tests showed that the pseudo-second-order model best fitted the adsorption process, with R2 values of 0.9999 for both dyes, confirming chemisorption as the rate-limiting step. The thermodynamic data indicates spontaneous, exothermic adsorption processes, with Gibbs free energy changes (∆G) for MB ranging from -11.265 to -10.82 kJ/mol and MO from -3.221 to -3.323 kJ/mol. Negative enthalpy changes (∆H) of -17.892 kJ/mol for MB and - 17.005 for MO show the exothermic nature of adsorption. The data proved effective removal of MB and MO dyes onto CMGG/PAAc hydrogels with better affinity for MB dye, making them excellent wastewater treatment adsorbents.

Microplastics in water resources: Global pollution circle, possible technological solutions, legislations, and future horizon

Beneath the surface of our ecosystems, microplastics (MPs) silently loom as a significant threat. These minuscule pollutants, invisible to the naked eye, wreak havoc on living organisms and disrupt the delicate balance of our environment. As we delve into a trove of data and reports, a troubling narrative unfolds: MPs pose a grave risk to both health and food chains with their diverse compositions and chemical characteristics. Nevertheless, the peril extends further. MPs infiltrate the environment and intertwine with other pollutants. Worldwide, microplastic levels fluctuate dramatically, ranging from 0.001 to 140 particles.m-3 in water and 0.2 to 8766 particles.g-1 in sediment, painting a stark picture of pervasive pollution. Coastal and marine ecosystems bear the brunt, with each organism laden with thousands of microplastic particles. MPs possess a remarkable ability to absorb a plethora of contaminants, and their environmental behavior is influenced by factors such as molecular weight and pH. Reported adsorption capacities of MPs vary greatly, spanning from 0.001 to 12,700 μg·g-1. These distressing figures serve as a clarion call, demanding immediate action and heightened environmental consciousness. Legislation, innovation, and sustainable practices stand as indispensable defenses against this encroaching menace. Grasping the intricate interplay between microplastics and pollutants is paramount, guiding us toward effective mitigation strategies and preserving our health ecosystems.

Bioinspired, Carbohydrate-Containing Polymers Efficiently and Reversibly Sequester Heavy Metals

Water scarcity and heavy metal pollution are significant challenges in today's industrialized world. Conventional heavy metal remediation methods are often inefficient and energy-intensive, and produce chemical sludge. To address these issues, we developed a bioinspired, carbohydrate-containing polymer system for efficient and selective heavy metal removal. Using ring opening metathesis polymerization, we synthesized polymers bearing amphiphilic glucuronate side chains capable of selectively binding heavy metal cations in mixed media. In samples containing high concentrations of heavy metals (>550 ppb), these polymers rapidly form a filterable precipitate upon metal capture, reducing the concentration of cation to <1.5 ppb within 3 min, as measured by inductively coupled plasma mass spectrometry. This system effectively removes cadmium ions from highly contaminated solutions to levels below the Agency for Toxic Substances and Disease Registry limit for Cd2+ in drinking water and selectively removes both Cd2+ and Pb2+ from lake water spiked with trace amounts of metal. Acidification triggers protonation of the glucuronate groups, releasing the heavy metals and resolubilizing the polymer. This capture-and-release process can be repeated over multiple cycles without loss of binding capacity. As such, this study introduces a novel class of recyclable materials with pH-responsive properties, offering potential for applications in water remediation and beyond.

Tailor-Made Polysaccharides for Biomedical Applications

Polysaccharides (PSAs) are carbohydrate-based macromolecules widely used in the biomedical field, either in their pure form or in blends/nanocomposites with other materials. The relationship between structure, properties, and functions has inspired scientists to design multifunctional PSAs for various biomedical applications by incorporating unique molecular structures and targeted bulk properties. Multiple strategies, such as conjugation, grafting, cross-linking, and functionalization, have been explored to control their mechanical properties, electrical conductivity, hydrophilicity, degradability, rheological features, and stimuli-responsiveness. For instance, custom-made PSAs are known for their worldwide biomedical applications in tissue engineering, drug/gene delivery, and regenerative medicine. Furthermore, the remarkable advancements in supramolecular engineering and chemistry have paved the way for mission-oriented biomaterial synthesis and the fabrication of customized biomaterials. These materials can synergistically combine the benefits of biology and chemistry to tackle important biomedical questions. Herein, we categorize and summarize PSAs based on their synthesis methods, and explore the main strategies used to customize their chemical structures. We then highlight various properties of PSAs using practical examples. Lastly, we thoroughly describe the biomedical applications of tailor-made PSAs, along with their current existing challenges and potential future directions.

Technological solutions to landfill management: Towards recovery of biomethane and carbon neutrality

Inadequate landfill management poses risks to the environment and human health, necessitating action. Poorly designed and operated landfills release harmful gases, contaminate water, and deplete resources. Aligning landfill management with the Sustainable Development Goals (SDGs) reveals its crucial role in achieving various targets. Urgent transformation of landfill practices is necessary to address challenges like climate change, carbon neutrality, food security, and resource recovery. The scientific community recognizes landfill management's impact on climate change, evidenced by in over 191 published articles (1998-2023). This article presents emerging solutions for sustainable landfill management, including physico-chemical, oxidation, and biological treatments. Each technology is evaluated for practical applications. The article emphasizes landfill management's global significance in pursuing carbon neutrality, prioritizing resource recovery over end-of-pipe treatments. It is important to note that minimizing water, chemical, and energy inputs in nutrient recovery is crucial for achieving carbon neutrality by 2050. Water reuse, energy recovery, and material selection during manufacturing are vital. The potential of water technologies for recovering macro-nutrients from landfill leachate is explored, considering feasibility factors. Integrated waste management approaches, such as recycling and composting, reduce waste and minimize environmental impact. It is conclusively evident that the water technologies not only facilitate the purification of leachate but also enable the recovery of valuable substances such as ammonium, heavy metals, nutrients, and salts. This recovery process holds economic benefits, while the conversion of CH4 and hydrogen into bioenergy and power generation through microbial fuel cells further enhances its potential. Future research should focus on sustainable and cost-effective treatment technologies for landfill leachate. Improving landfill management can mitigate the adverse environmental and health effects of inadequate waste disposal.

Biopolymeric Nanocomposites for Wastewater Remediation: An Overview on Recent Progress and Challenges

Essential for human development, water is increasingly polluted by diverse anthropogenic activities, containing contaminants like organic dyes, acids, antibiotics, inorganic salts, and heavy metals. Conventional methods fall short, prompting the exploration of advanced, cost-effective remediation. Recent research focuses on sustainable adsorption, with nano-modifications enhancing adsorbent efficacy against persistent waterborne pollutants. This review delves into recent advancements (2020-2023) in sustainable biopolymeric nanocomposites, spotlighting the applications of biopolymers like chitosan in wastewater remediation, particularly as adsorbents and filtration membranes along with their mechanism. The advantages and drawbacks of various biopolymers have also been discussed along with their modification in synthesizing biopolymeric nanocomposites by combining the benefits of biodegradable polymers and nanomaterials for enhanced physiochemical and mechanical properties for their application in wastewater treatment. The important functions of biopolymeric nanocomposites by adsorbing, removing, and selectively targeting contaminants, contributing to the purification and sustainable management of water resources, have also been elaborated on. Furthermore, it outlines the reusability and current challenges for the further exploration of biopolymers in this burgeoning field for environmental applications.